The type 2 diabetes drug metformin could prevent cancers from becoming resistant to chemotherapy, a study from Canada suggests.

Previous research has shown the drug's ability to slow the growth of tumour cells, and now a study by University of Saskatchewan has found that the blood glucose-lowering drug has the potential to reduce and reverse resistance to treatments in breast cancer cells.

These findings are significant because multidrug resistance (MDR), which occurs when chemotherapy fails, normally results in a terminal diagnosis. Resistance to one drug often leads to defiance to multiple treatments, affecting people with blood cancers as well as solid tumours, including breast cancer.

It is hoped that these results could one day pave the way to preventing and reversing resistance to cancer treatments.

Research has already demonstrated metformin's ability to be antiproliferative, that is to inhibit the growth and spread of cancer cells. There is a 31 per cent reduction in the emergence of new cancers in people with diabetes taking the medication who have existing cancer, studies have shown. Metformin has also been shown to improve breast cancer survival rates.

In this latest research, the scientists investigated the process behind metformin's antiproliferative effect and also looked at whether the drug could have any benefits in preventing MDR.

The researchers tested breast cancer cells and discovered that metformin had a positive antiproliferative effect on cells resistant to a chemotherapy treatment called doxorubicin and delayed, prevented or reversed MDR in cells pretreated with metformin.

"We have demonstrated that metformin monotherapy has an antiproliferative effect on multiple cell lines, including those selected for resistance to doxorubicin, in a dose-dependent manner," said the study authors.

"The effect is also observed when metformin is used in combination with other anticancer treatments in breast cancer cells. Our findings are consistent with the growing literature base demonstrating metformin's ability to slow the growth of tumour cells in vitro."

Now the research team plans to answer the question of whether metformin's impact can be demonstrated over a longer period.